Kingston PC6400CL4 and PC8500CL5 2GB Memory Kits Review

Memory by thorgal @ 2007-02-21

When it comes to high performance memory, Kingston has a name to keep up in the business. We already took some memory kits from Corsair, Team Group and OCZ for a spin, but Kingston was noticeably absent. About time we set this right, and we do this today by looking at two of their products: the PC6400CL4 and PC8500CL5, both 2Gb kits. Let´s see how they stack up against some fierce competition...

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Overclocking Results

A word on Asus P5B-deluxe performance

The motherboard that we are using for all our memory testing is the Asus P5B deluxe/wifi-AP, a motherboard equipped with the Intel 965 chipset. We chose specifically this motherboard because it is capable of attaining very high front side bus speeds compared to motherboards equipped with the Intel 975 or (older) nVidia chipsets. Among the 965 motherboards, the Asus is also one of the better performing boards, often reaching FSB speeds of more than 500FSB. Of course, when we want to test memory overclocking, we need a motherboard that is capable of this high FSB, and one that is compatible with high frequency ram (the 975 chipset is known to give problems with ram over 1000Mhz, sometimes).

Now how does the Intel 965 chipset reach these high front side bus speeds? You must realize that, when you start pumping up the FSB of your motherboard, you are actually overclocking your chipset. Just like memory, chipsets have standard timings and standard voltages, and when you're overclocking you can give a little more voltage to the chipset, in order to make it scale higher. Normally, once you hit 380-430FSB on the Intel 965 and the 975 chipset, you hit an overclocking wall (unless you do some more exotic, warranty voiding trickery of course...). How does Asus reach 500FSB than? That’s where Tony "Bigtoe" comes in : he has been hard at work to get the public familiar with the technology behind the 965 chipset, and one of the things he found out was that the P5B automatically relaxes (slows down) the timings of the chipset itself in order to be able to scale above 400FSB. There seem to be certain "sets" of timings which are implemented at different FSB settings, and these sets are called "straps". The Asus P5B now sets a different strap when you boot at 400+FSB, than when you boot at 400-FSB, the 400+ strap being the slower of the two. This obviously has a direct influence on your memory bandwidth and on the entire performance of your PC. This will show up in this review as well, when we're looking into the performance of the Team Group's ram, which scaled beyond 400FSB on our settings, and in the process gives worse results than you would actually expect...

Take a look at this and this thread by Tony Bigtoe over at the support forums of BleedinEdge, and also at this thread at the XtremeSystems forums. Finally, here's a link to Tony's P5B-deluxe tweaking guide, from the excellent Tech Repository forums which have been recently founded by Kris "Freecableguy" and Tony "Bigtoe". These threads are in my personal opinion obligated reading for anyone considering to buy a top performing memory kit, just to understand the performance of your PC setup.

Overclocking performance

The goal of this section of the review is to look how far the modules are willing to go. For this we played around with different memory latencies a bit, to end up with the best cas 3, cas 4 and cas 5 performance of these particular modules.

In our experience, Orthos is the most demanding stability test we can run. Orthos is the dual core version of the better known Stress Prime 2004, or SP2004 in short, which in his term is based upon the famous "Prime95" code. Even when all tests succeeded, Orthos testing would sometimes fail. On the other hand, when Orthos succeeded in running for about 1/2 hour, other tests would (almost) never become a problem.

Kingston PC6400C4

As the specifications on the previous pages pointed out, the Kingston PC6400 kit is rated to work at speeds of 800Mhz DDR2, and this with 4-4-4-15 timings and at a voltage of only 2.0V. For the testing of OC performance, we try never to exceed the warranted voltage, which in this case was a little difficult, as Kingston does not provide us with details of any voltage or "over-voltage" warranty. We applied voltages up to 2.15V, which should be safe for any DDR2 memory module out there. The memory voltages were also monitored by a multimeter in order to verify that they are accurate when testing. Anyway, because the memory chips that are present on the PC6400 kit are made by Elpida, we already know from past experience that overclocking these chips by increasing voltage offers little to no additional headroom. These chips like rather low voltage of 1.8-2.2V, giving them any more really does them more harm than good. Finally, 2.15V for the memory is something almost every board is capable of delivering, making this setting available to almost everybody.

Let's start with the rated timings, and see how far the modules can be overclocked at a cas setting of 4 cycles.

After playing around with the sub timings a little, we got our PC6400 kit Orthos stable at 880Mhz DDR2, while applying 2.15V to the chips. On standard voltages the results were barely lower, reaching 860Mhz DDR. In the end, we get a 10% increase in speed at the standard timings of 4-4-4. If we compare this to the OCZ PC6400 Special Ops Edition Urban Elite's performance, Kingston falls a little short.

Next up is the cas 3 setting, where the Kingston PC6400C4 reached 740Mhz DDR with 3-3-3-10 timings, still at 2.15 Volts. In this case Kingston beats the OCZ kit by 50Mhz, a great achievement. This theoretically means you could run your PC setup at 370FSB, while maintaining a 1:1 memory ratio (if your cpu and motherboard are capable of these speeds of course) and keeping your ram at 3-3-3 timings.

Finally, let's have a look at the cas 5 performance. Well, I saved the best for last, because I'm very pleased to see this kit surpass the 1000Mhz DDR mark, and reach a very respectable 1020Mhz DDR. This speed is fully Orthos stable, while using 5-5-5-15 timings, and applying 2.15 Volts to the memory. The result is just a little lower than we got out of the OCZ Urban Elite kit, but it's very nice to be able to get over 25% extra speed out of any memory product.

Below are the screenshots of the Orthos runs at the maximum memory speeds we achieved, for the different cas and system settings.

Madshrimps (c) Madshrimps (c) Madshrimps (c)

Left to right (click to open) : Maximum CAS3, CAS4, CAS5

Kingston PC8500C5

The Kingston PC8500 kit is rated to work at speeds of 1066Mhz DDR2, and this with 5-5-5-15 timings at a voltage of 2.2V. Again, when testing we try to comply with the warranties that are provided by the manufacturers, but Kingston does not provide us with details of any voltage warranty in this case either. For the PC8500 kit we applied voltages up to 2.25V (the P5B-deluxe has no 2.2V setting), which should be on the (very) safe side for the Micron memory modules which are present on these sticks.

Then again, when we look at Micron memory chips, there were some strange results in this case when trying the different voltages. Normally, Micron scales very well with additional voltage, certainly from 2.2V to 2.4V and even way past that. In this case results were not that clear : after our standard benchmark tests were done, I tried voltage increases up to 2.45V, but got only 5 extra Mhz out of the modules. This means that our tests at 2.25V give a good impression of the maximum results that can be attained. Of course, I'm not talking about voltages up to 2.8V or 3.0V now : such voltages are not the scope of this review. Scaling could improve with even higher voltages if you have the "guts" to try it...

Let's first look at the rated timings again and there's certainly some good news here. At 2.25V, the Kingston PC8500 kit went all the way up to 1152Mhz DDR, with timings of 5-5-5-16. This makes this kit the third fastest kit we ever tested. This is an absolutely great result, even more so when you consider the rather low voltage that was applied. I had hoped the memory would scale even better when a higher voltage was applied, but as I explained in the former paragraph, this was not the case. But as I said, 1152 Mhz is a very respectable result only obtained so far by more expensive kits.

Next up is the cas 4 setting: at cas 4 our memory reached 1008Mhz DDR with 4-4-4-16 timings, and 2.25 volts. This result was, certainly compared to the excellent cas 5 results, rather disappointing. Compared to the other Micron-equipped memory modules, the Kingston module is at the bottom of the pack. Reason for this could certainly be the rather low voltage we applied (for Micron chips), but as we explained, voltage scaling was also not as expected. Could it be that these chips are a newer brand of Micron, or are they just selected for cas 5 performance?

Finally, at the cas 3 setting, we fall just short of the 800Mhz DDR mark. With 797Mhz at 3-3-3-10 and 2.2V we hit the expected performance for Micron chips at the specified voltage, but as with the others cas 4 setting, couldn't better it by increasing voltages. The modules are at the back of the Micron pack again, however, don't forget that this is still great performance, which cannot easily be obtained by lower rated memory (without Micron chips).

Again you can find the screenshots of the Orthos runs below, at the maximum memory speeds we achieved, for the different cas and system settings.

Madshrimps (c) Madshrimps (c) Madshrimps (c)

Left to right (click to open) : Maximum CAS3, CAS4, CAS5

On to the benchmark results now ->
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Comment from Sidney @ 2007/02/21
Go for the lowest price point is still the best choice?
Comment from jmke @ 2007/02/21
best choice for who? If you're concerned about your budget, going for lowest price point is always the best choice
Comment from Sidney @ 2007/02/21
Indremental Money spent versus incremental performance/value received.
Comment from jmke @ 2007/02/21
for none OC'ers, this article still is true

cheapest PC6400 DDR2 ram more than enough to satisfy COre 2 bandwidth needs
Comment from Sidney @ 2007/02/21
Agree; unless you get a processor that can do +500 FSB everytime, finding mobo and memory become secondary and relatively easier than the formal.
Comment from jmke @ 2007/02/21
I think most E6300 can reach 500+, just need a mobo that can do it
having negative FSB:MEM divider also helps